Resolution:
On a Unix machine, there is two ways to launch tibcoAdmin (or tra)
1st way : under $tibco_home/administrator/2.0 you launch the setenv.sh that will set correctly all the system variables. Then you can launch under
$tibco_home/administrator/2.0/bin ./tibcoadmin (the option --propFile tibcoadmin.tra is not necessary when the name of the .tra file is the same as the name of the wrapper (tibcoadmin in our case)

We also provide rcscript :

2nd way : Go to $TIBCO_HOME/tra/1.0/tools/rcscripts and launch initTIBCOAdmin